The SSC is a good option. Calder did a comparison of the control algorithms
for the Danfoss AEO, Frigbot SSC and the Isotherm ASU in the October 2004
Professional Boatbuilder. Of the three the SSC seemed to have the most
sophisticated program. Works similar to the AEO by monitoring run times and
adjusting speed but the SSC has an "ideal" profile that it tries to fit to
over time. The Isotherm unit really just watches the system voltage and
turns the compressor to high speed when it sees the system is being charged.
Not necessarily the best for temperature control but saves the most battery
amps.

I have an idea for a program that was sort of a blend of all three and could
do a lot more but decided that I didn't want to risk a frige full of spoiled
food because of a programming error. :-)

An interesting side note: I have met several folks who have been cruising
for a long time that complain that their compressors run to long and want to
speed them up when in actuality they are most efficient when they run 59
minutes out of every hour.

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

wrote in message
oups.com...
I was present during 105 degree ambient tests of the AEO in freezers
and was impressed with its performance but if you can not find them,
the next best thing is a Frigoboat SSC. I have one on my test bench
and it performs much like the AEO even adjusts for day night economy.
The SSC also has the LED built in including six differant speed LEDs.
There are a series of tests on the SSC in my 12/24 volt book. The BD50
will require a soft start feature if operated at max RPM in a warm
climate, both of these controllers have soft start features.
Dick

Oops! Acid flux depends on being washed off after soldering. Might this be
a problem?

Roger

http://home.insightbb.com/~derbyrm

"Glenn Ashmore" wrote in message
news:mUiQf.497330$0l5.326643@dukeread06...

snip

With my small diameter tube I am not to worried about the bond but I will
sand blast the whole bolt frame/condenser assembly and paint the tubing
with an acid flux formulated for tinning copper pots. I found that the
copper/nickel wets out much better with it than regular acid solder flux.

Not really. Because there is so much mass the lead will take over 3 hours
to start solidifying. The flux should float to the surface and be washed and
ground away in the post casting operations.
--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

"derbyrm" wrote in message
news:V9HQf.854379$xm3.37448@attbi_s21...
Oops! Acid flux depends on being washed off after soldering. Might this
be a problem?

Roger

http://home.insightbb.com/~derbyrm

"Glenn Ashmore" wrote in message
news:mUiQf.497330$0l5.326643@dukeread06...

snip

With my small diameter tube I am not to worried about the bond but I will
sand blast the whole bolt frame/condenser assembly and paint the tubing
with an acid flux formulated for tinning copper pots. I found that the
copper/nickel wets out much better with it than regular acid solder flux.

The Isotherm ASU system is a progressive speed adjustment based on
evaporator temperature feedback and efficiency adjustments has nothing
to do with voltage. The Automatic Speed Up function is an extra bonus
to the automatic temperature speed control. Advancing compressor speed
when a charging current is available will store additional surplus
energy in the system's holding plate. I do not see how anyone could
believe that the SSC is better than the ASU
from the tests that I have run. I recommended Danfoss's AEO first as
it is a Completely new module. My second choice was Frigoboat's SSC
over Isotherm's ASU for two reasons, Isotherm will not sell their
unit separate you must buy a complete system and the ASU has limited
control when the tropical heat load exceeds its automatic adjustment
range.

Interesting. Calder's article said nothing about the ASU monitoring
anything but system voltage. My thought was that the ideal control would
monitor box temperature, evaporator temperature and cycle time. That way it
could sense when the box had been loaded with warm items and react faster to
frequent opening. Strictly time based algorithms take several cycles to
adjust to changing conditions. Reading the latest Isotherm literature it
looks like the ASU comes pretty close but it seems oriented towards holding
plates. Apparently the ASU replaces the whole power unit where the SSC just
varies the thermostat circuit resistance.

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

wrote in message
ups.com...
The Isotherm ASU system is a progressive speed adjustment based on
evaporator temperature feedback and efficiency adjustments has nothing
to do with voltage. The Automatic Speed Up function is an extra bonus
to the automatic temperature speed control. Advancing compressor speed
when a charging current is available will store additional surplus
energy in the system's holding plate. I do not see how anyone could
believe that the SSC is better than the ASU
from the tests that I have run. I recommended Danfoss's AEO first as
it is a Completely new module. My second choice was Frigoboat's SSC
over Isotherm's ASU for two reasons, Isotherm will not sell their
unit separate you must buy a complete system and the ASU has limited
control when the tropical heat load exceeds its automatic adjustment
range.

The reason we want to control compressor speed is to use the lowest
amount of daily onboard power and maintain the box temperature we want
at all times. We by a compressor that can produce the results we want
and generally more capacity output most of the time. Cutting down on
capacity by lowering compressor speed improves SCOP (System Coefficient
Of Performance). Whenever the box temperature can be maintained at the
compressors slower speeds and still have it cycle off the end result
will be fewer daily amp-hrs consumed. What all three of these speed
controllers do is compensate for day night and seasonal temperature
changes. They all will change speed but slowly when warm product is
added to the box. The SSC and ASU both can be set to manual to speed up
the cooling process. I believe only the SSC will provide actual
compressor speeds at the panel. All of these units change the milliamp
flow in the thermostat circuit to control compressor speed.

Richard, You got me thinking (which can often be dangerous).

Reading further on the ASU Isotherm spends a lot of time talking about
monitoring system voltage and increasing compressor speed when there is
extra power available i.e. battery charging. This is great for holding
plates but of no particular value in evaporator systems. The one thing I
see that the ASU has over the AEO or the SSC is that it looks at evaporator
temperature as well as run time to optimize compressor speed.

The key to maximum efficiency in an evaporator system is to keep the
compressor running as long as possible as slow as possible. In process
control systems the easiest systems to control are the ones that are stable
or change slowly. A top opening refrigerator qualifies as long as you don't
add a lot of warm items or accidentally leave the hatch open. The AEO works
fine in this situation but will require an hour to adjust to a major
variation like adding a lot of warm items and then it has to start readjust
back to normal over several cycles after the box recovers. The AEO
algorithm also reaches equilibrium at 32 minutes run time. It seems to me
that with a well insulated box that stayed under the on point for longer
than 6 or 7 minutes the speed would not get as slow as it could. The SSC
has a target of 50 minutes run time in an hour which might give a better
overall COPE.

I would like to see a system with 3 set points; off, on and exception and
maybe an adjustable duty cycle. As long as the box stays below the
exception point the control would adjust compressor speed to maintain a 90
to 95% duty cycle. If the box warmed above the exception point the
compressor would run at high speed until the box recovered but that cycle
would not be used to calculate the normal run speeds. That way the control
could react quickly to new loads and return to normal operation as soon as
the box recovered. The duty cycle could also be adjusted downward when the
boat was on shore power or charging and power was not at a premium.
--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

wrote in message
ups.com...

The reason we want to control compressor speed is to use the lowest
amount of daily onboard power and maintain the box temperature we want
at all times. We by a compressor that can produce the results we want
and generally more capacity output most of the time. Cutting down on
capacity by lowering compressor speed improves SCOP (System Coefficient
Of Performance). Whenever the box temperature can be maintained at the
compressors slower speeds and still have it cycle off the end result
will be fewer daily amp-hrs consumed. What all three of these speed
controllers do is compensate for day night and seasonal temperature
changes. They all will change speed but slowly when warm product is
added to the box. The SSC and ASU both can be set to manual to speed up
the cooling process. I believe only the SSC will provide actual
compressor speeds at the panel. All of these units change the milliamp
flow in the thermostat circuit to control compressor speed.

Glenn, You want a climate control for a jet aircraft that has
anticipators to make a correction in advance of the actual temperature
change. Heat transfer in a box is slow because static air is the
conductor from the heat source to the evaporator, where heat it is
drawn away by a small compressor. Frigoboat's SSC will give you
every thing you need but you my need to switch to manual and advance
speed before adding a large volume of warm product. I have included a
number of gadgets in my 12 volt book that can shorten the reaction time
by, increasing airflow across evaporator, starting compressor or
speeding it up when a charging voltage above 13.2 is present. You
don't need a holding plate in a refrigerator to store surplus energy,
product in the box and the box itself can store one Btu per degree per
pound, of material. In a freezer when the product is already frozen
additional energy stored is only ½ a Btu per degree per pound or 144
Btu per pound added when when the phase change from a liquid to a solid
occures.


....

I have probably spent to much time working with PID and fuzzy logic
controllers. :-) There is so many sophisticated off the shelf industrial
process controllers these days I can see the day when we will see a marine
refrigeration controller that will do a lot more than we can think of.

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

wrote in message
ups.com...
Glenn, You want a climate control for a jet aircraft that has
anticipators to make a correction in advance of the actual temperature
change. Heat transfer in a box is slow because static air is the
conductor from the heat source to the evaporator, where heat it is
drawn away by a small compressor. Frigoboat's SSC will give you
every thing you need but you my need to switch to manual and advance
speed before adding a large volume of warm product. I have included a
number of gadgets in my 12 volt book that can shorten the reaction time
by, increasing airflow across evaporator, starting compressor or
speeding it up when a charging voltage above 13.2 is present. You
don't need a holding plate in a refrigerator to store surplus energy,
product in the box and the box itself can store one Btu per degree per
pound, of material. In a freezer when the product is already frozen
additional energy stored is only ½ a Btu per degree per pound or 144
Btu per pound added when when the phase change from a liquid to a solid
occures.


....

On Sun, 12 Mar 2006 11:45:50 -0500, "Glenn Ashmore"
wrote:

I have probably spent to much time working with PID and fuzzy logic
controllers. :-) There is so many sophisticated off the shelf industrial
process controllers these days I can see the day when we will see a marine
refrigeration controller that will do a lot more than we can think of.

Glenn, following along in this discussion, it sounds like you picked
an evaporater unit instead of a holding plate system. If so, I'm
curious why you did that. Perhaps my situation is different because I
have a large generator available, but I really like the idea of only
needing to run the compressors for a few hours per day.